The present invention relates to a method and apparatus for providing backup electrical power to a community of homes.
In the traditional mode of providing electrical power to homes, power is delivered from a centralized location to neighborhoods by way of power lines. The destinations for power, such as homes and businesses, are arranged on these power lines in a “serial” fashion; that is, the power lines are run along a line that generally parallels the houses on the streets of the community. Each location taps off of the power line, which feeds each location. Thus, a multitude of homes within a community, neighborhood or even town may be dependent upon a single power line or a small group of power lines.
Obvious downsides to this current mode of power delivery exist. Since all the locations powered by the lines are fed from one location, a break in the power line, whether by felled trees, wind, blown transformers or other causes, may interrupt power from being delivered to numerous locations. This obviously results in at best, inconvenience, and at worst, may be life-threatening for those who require power for items such as respirators or heating their homes.
To combat this, several concepts have been advanced. One of these is to bury power lines in the ground as opposed to mounting them on poles where they are more exposed to the elements. This largely eliminates problems caused by wind or fallen objects, but is only as effective as far as the power lines are buried. Should, for example, a tree fall on an above ground line feeding an area with buried cables, power utility service will still be lost. The recent hurricanes that struck the U.S. Gulf Coast provide numerous examples of areas that were without power for weeks at a time, even though no damage or only minor damage may have occurred in their immediate vicinity, showing a clear need for backup power in areas that are likely (and often) without power.
Another method of dealing with loss of power is through the use of generators. Small, portable generators can be used with relative ease and are not particularly expensive to maintain, but can only power a few appliances and lights at a time, and must be used at each location without power. While better than nothing, most of these generators are for emergency use, and not suitable to have a household function normally as it would under full power. In addition, these generators require some understanding of how electricity is transmitted, yet they are often installed by persons without much appreciation or understanding of how electricity transmission lines work. Damage to electrical appliances and home electrical lines from improperly installed generators is not uncommon. House fires resulting from such damage is an all too frequent occurrence. Moreover, the wake of a natural disaster is a particularly poor time for a fire, as the demands on emergency workers will already be quite high.
Whole-house generators which are permanently installed in homes may be employed as an alternative. These larger generators overcome much of the lack of power in smaller generators, and can be setup to run automatically without much user intervention. However, these generators cost much more than portable generators, and require significant maintenance by the homeowner. Even considering the benefits, these larger generators must still be installed at each home to be powered, with all of the problems addressed above that can arise from improper installation.
With either of these generator solutions, another problem is introduced by virtue of the generator's connection to an electrical system, that of backfeeding. Backfeeding is the introduction of electrical current to power lines from a service location rather than to it. For example, if power is out to an area, and a generator is connected to a home and operating, it may be installed so that it is delivering power back to the lines that ordinarily feed it. While such installations are improper, they are unfortunately relatively common. The danger is that power company employees who are in contact with these lines may be injured or electrocuted by the power being delivered to lines that were thought to be dead. Backfeeding is one of the biggest sources of injury to utility company workers.
All of these aspects of the current state of the art lead to an increased need for a backup power system for communities meeting the following objectives.